The layered structure of Additive Manufacturing processes results in a stair-stepping effect of the surface topographies. In general, the impact of this effect strongly depends on the build angle of a surface whereas the overall surface roughness is caused by the resolution of the specifi c AM process. The aim of this work is the prediction of surface quality in dependence of the part building orientation. Furthermore, these results can be used to optimize the orientation of the part to get a desired surface quality for functional areas or an overall optimum. In AM the build height is most often a cost factor, therefore the part orientation tool takes not only the predicted surface quality into account. The job height is an optimization objective for this tool as well.
Based on experiments a surface roughness database was generated. To support this database an additional surface roughness Rz simulation tool was developed (Figure 1a / 1b). Usually not every area of a part can be optimized, as the surface quality is highly dependent on the build angle. Therefore, a pre-assignment of functional or important areas takes place for the orientation simulation. The selected surfaces get an increased weighting factor for the preferred build alignment. The model uses the digital STL format of a part as this is essential for all AM machines. Each triangle is assigned with a roughness value and by testing different orientations an optimized position can be found. Even if this tool is validated and build on the LS process, this method can be applied to all AM technologies.
With the alignment optimization tool for AM processes, which uses a surface roughness database and build height as optimization objectives, it is possible to validate the part orientation for AM parts.